This invention relates generally to linear accelerators and, more particularly, to applications of induction-type linear accelerators that generate beams of charged particles, such as electrons, of very high energies. There are basically two types of linear accelerators, one employing radio-frequency (rf) energy to accelerate electrons or other particles, and the other operating on an induction principle. In accelerators of the induction type, electrons are accelerated by means of a series of induction cores through which they are passed. When each core is activated with a large electrical pulse, it functions in the manner of a transformer, inducing current flow in its "secondary winding," which is the stream of electrons passing along the axis of the core. A beam of electrons, or more precisely a stream of packets of electrons, is accelerated in each of a series of such cores, until the electrons reach a desired energy or velocity level.
The high-speed electrons are put to a variety of uses, such as in the analysis of subatomic particles, in free-electron lasers, or in the irradiation of food. In many cases, however, the accelerated electrons still have a very high energy after they have been put to use. Typically, the remaining high-speed electrons are "dumped" into an absorbent material, such as graphite. Although this approach has been satisfactory for most purposes, in recent years there has been a requirement for electrons of higher and higher energies, and dumping of extremely high-energy electrons has the important disadvantage that the absorbent material employed will become significantly radioactive. Appropriate handling and treatment related to radioactive substances will be needed in these cases.
Accordingly, there is a need for a different approach to the handling of high-energy electrons or other charged particles produced in an induction linear accelerator. The present invention satisfies this need.